Ignition mixture



Patented Feb. 20, 1940.

EGNKTION TUBE No Era. Application .lannary 21, 1930, Serial No. 252,200

8 Claims. (Cl. 52-4) This invention relates to an improved ignitioncompound adapted more particularly for use in electric blasting caps.

It is well known that electric blasting caps include a shell containingan explosive charge comprising a base charge and a priming charge thatare detonated by means of an electric firing assembly consisting of abridge wire from which extend a pair of lead wires. The cap shell I: isclosed by waterproofing and a seal. Further, the art often employs,.within electric blasting caps, ignition compounds that are superimposedupon the explosive charge to facilitate the ignition of the explosivecharge. The passage of an electric current through the firing assemblyignites the ignition charge which in turn causes the detonation of theexplosive charge.

The general requirements of a satisfactory ignition compound are that itbe easily ignited by 9 a small amount of heat and that it will, whenignited, cause positive detonation of the explosive charge. Further an-ignition compound, for use in electric blasting caps, should not, whenignited, detonate and interrupt the firing circuit 5 as is the case ofdetonating compounds, for example, diazodinitrophenol and mercuryfulminate, but should provide a very short increment of time between theapplication of the current and the interruption of the firing circuit,thereby allowing those caps, in the series, with individual slow-firingcharacteristics to become ignited. This firing characteristic ofignition compounds allows an increase in the number of blasting capsthat may be fired in series with a definite firing current.

It is the object of this invention to produce an improved ignitioncompound suitable for use in electric blasting caps. A further objectof'this invention is to provide an ignition compound with o firingcharacteristics that will allow an increased number of electric blastingcaps to be fired in series with a definite circuit. Further objects willappear hereinafter.

Now in accordance with this invention, I have 5 found that I may producean ignition compound which, when used in electric blasting caps, has alow critical firing current, is readily ignited by electrical means, andinsures positive detonation of the explosive charge, by intimatelyadmixing a detonating compound with an oxidizing agent and a fiameproducing agent.

Ihe proportions of ingredients-in my ignition composition may varywidely but are desirably within the following ranges; detonating com- 5pound about 10% to about 20%, oxidizing agent about 10% to about 50%,and a flame-producing agent about 35% to about 75%. It is also desirableto have the ingredients in a finely divided dry state before they areadmixed by any suitable means. 5 Among the detonating compounds that Imay use in accordance with this invention are, for example,'diazodinitrophenol or mercury fulminate. To insure complete andintimate admixing, it is desirable to control the particle size 10 ofthe detonating compound being used and I have found that favorableresults may be obtained with diazodinitrophenol by using a materialhaving a particle size within the range of about 25 to about 200 micronsin diameter and preferably about 50 to about 100 microns in diameter.Further when using mercury fulminate, I find it desirable to usematerial that will pass a #0 bolting cloth, 38 openings per lineal inch.

Among the oxidizing agents that I may .use in accordance with thisinvention are, for example, barium nitrate, potassium nitrate, potassiumchlorate or the like. I prefer to screen the oxidizing agent to be usedthrough a 60 mesh sieve as material of such size allows very readyadmixing with the other ingredients to be used.

Among the flame-producing agents that I may use in accordance with thisinvention are, for example, double base smokeless powder grains 1 that,preferably, will pass a 60 mesh screen and will be retained on a 72 meshscreen; single base smokeless powder grains that, preferably, will passa 100 mesh screen; nitrolactose, nitromanite, and nitrostarch grainsthat, preferably, will pass a 60 mesh screen.

Having now described in a general way the nature and purpose of myinvention and the ingredients that I may use therein, I shall proceedwith a more detailed description of specific examples thereof.

I prepared an ignition compound in accordance with this invention byadmixing 15 parts by weight of diazodinitrophenol having a particle sizeof about to about 100- microns diameter with parts by weight of doublebase smokeless 45 powder, all of'which will pass a mesh screen and willbe retained on a 72 mesh screen, and 30 parts by weight of bariumnitrate. The dry ingredients were mixed on a triangle mixing cloth untilan intimate admixturewas obtained. 50

A marked improvement in performance was obtained from electricalblasting caps containing a charge of the ignition compound of theaforedescribed specific example. The improvement may be definitely shownby a comparison of re- 5 sults obtained upon firing electrical blastingcaps containing the aforesaid ignition compound and results obtainedupon firing regular commercial electric blasting caps containing no suchignij tion compound.

In the following table the electric blasting caps were fired in seriesby a small commercial blasting machine.

Table 1 Number otragulu commercial electric blasting Number of vinseries failures occur-cu- It is apparent from the results given inTable 1 that electric blasting caps containing an ignition chargeprepared as indicated in the aforedescribed specific example have firingcharacter-- istics superior to those of the regular commercial electricblasting caps, It is well known to those skilled in the art that thenumber of caps that it is possible to fire will vary with the individualblasting machines used for testing. However, any particular blastingmachine will give results which will-show the same relative improvementof the caps of this invention over commercial caps shown in Table 1.

Aiiother specific example of my ignition mixture consists of anadmixture of diazodinitrophenol, barium nitrate and 55% nitrolactose.'I'he diazodinitrophenol and barium nitrate of this mixture have thesame particle size as the materials used in the preceding specificexample and I have used nitrolactose that will pass a 60 mesh screen.Results obtained by using this admixture in electric blasting capsclosely approximate those results given for the ignition admixture ofTable l.

While Ihave admixed the dry ingredients of my ignition compound on atriangle mixing cloth,

, I contemplate other suitable means of mixing these ingredients thatwill be well hown to those skilled in the art. I may also mix the ingre-'dients in a dry or wet state dependent upon the 1 means empl yeIgnition compositions in accordance with my invention will be found tobe relatively free fiowing and therefore easy to load into the electricblasting cap shells. 'I'hese ignition compositions will also be readilyignitable by electrical means and effective for detonation of theexplosive charge. While I have specified that my ignition compositionsare for use in electrical blasting caps and are to be fired byelectrical means, it is to be understood that I contemplate the use ofmy ignition compositions in other firing devices that are ignited byelectric means or by the spit of a safety fuse.

It will be understood that the details and examples given hereinbeforeare illustrative only, and in no way limiting on my invention as broadlydescribed hereinbefore and in the appended claims.

What I claim and desire to protect by Letters Patent is:

1. An ignition. composition comprising as ingredients,diazodinitrophenol, an oxidizing agent and a flame-producing agent fromthe group consisting of a nitrated carbohydrate and smokeless powder.

2- An ignition composition comprising as ingredients,diazodinitrophenol, about 10 to about 20% an oxidizing agent, about 10to about 50%; and a flame-producing agent from the group consisting of anitrated carbohydrate and smokeless powder, about to about 75%.

3.-An ignition composition comprising as ingredients,diazodinitrophenol, about 10 to about 20%; barium nitrate, about 10 toabout and smokeless powder, about 35 to about 75%.

4. An ignition composition comprising as ingredients,diazodinitrophenol, about 10 to about -20%; potassium chlorate, about 10to about 50%; and nitrolactose, about 35 to about 75%.

5. Anignition composition comprising as ingredients, diazodinitrophenol,about 10 to about 20%; barium nitrate, about 10 to about 50%; and adouble base smokeless powder, containing about 15 to about 35%nitroglycerin, about 35 to about 75%.

6. An ignition composition comprising as ingredients diazodinitrophenolabout 15%, barium Eiitrate about 30%, and smokeless powder about 5%. r'7. An ignition composition comprising as ingredients diazodinitrophenolabout 10% to about 20%, barium nitrate about 10% to about 50%, andnitrolactose about 35% to about 75%.

8. An ignition composition comprising as ingredients diazodinitrophenolabout 15%, barium nitrate about 30%, and nitrolactose about HORACE I.ETCHEILS, JR.

